I've got a Rogue Engineering cat back so it was already pretty aggressive sounding and I can detect no difference...maybe when I can finally exceed 4,500 I'll be able to notice a change. Not expecting any. At idle, there's a very slight S/C rattle which is apparently normal. Blip the throttle and there's a bit of S/C whistle which sounds really cool. Both are nearly un-noticeable with hood closed and can't be heard from drivers seat. For all practical purposes, car is a sleeper.

Sounds killa. I've got the UUC RSC36 exhaust system. Currently, I have no cold air intake. I bet there will be an auditory difference once you begin to accelerate under a load (pedal to the metal at 5,000 RPM). Most of the blown E46 M3s that I've ever listened to at Bimmerfest are way more aggressive-sounding than stock...

This is what mine looks like. I have been a BMW fanatic since 1977 (mom& dad's first E21 318is they bought as a pair):

I have been with BMW as a retailer on and off since 1987. The E36 M3 is my all-time favorite Bimmer....